The present invention relates to a combination slide retainer and position sensing switch for injection molds.
An injection molding machine includes stationary and movable mold halves mounted therein. The movable mold half is sidlingly advanced by the molding machine, between an open and a closed position relative to the stationary mold half. It is often necessary or desirable to form all or part of the mold cavity on slides which move laterally (ninety degrees) relative to the direction of opening and closing of the mold halves to facilitate the forming of certain side details on the molded part such as undercuts or laterally extending holes. Typically, angled cam pins mounted on the stationary mold half cooperate with inclined bores in the slides to advance the slides between an open and closed alignment laterally relative to the mold halves as the mold halves are advanced between open and closed alignments.
In a mold cycle, the mold halves are first advanced to a closed alignment, such that the slides similarly advance to a closed alignment forming the mold cavity. Plastic is injected into the mold cavity through a nozzle to form the molded part. After a preset amount of time, calculated to permit the molded part to cool sufficiently, the movable mold half is advanced away from the stationary mold half causing the slides to advance laterally relative to the movable mold half and the molded part. Ejector pins or sleeves, are then advanced out of the movable mold half to engage and eject the molded part out of the mold. The ejector pins or sleeves are retracted and the cycle is repeated.
During the molding cycle, it is important to maintain the slides in the open position while the molded part is ejected and until the movable mold half is advanced back toward the stationary mold half, to prevent damage to the mold. If a slide slips out of the open position, before closing of the mold, the inclined bore in the slide will not line up with the angled cam pin when the mold is closed, which can result in damage to the slide, the cam pin or both. In addition, it is important to be able to verify that the slides have advanced to and remain in the open position before the ejector pins or sleeve are advanced out of the movable mold half. If a slide failed to advance to the open position when the mold halves were opened or slipped back to the closed position before the ejector pins or sleeves are advanced out of the movable mold half, engagement of the slide by an ejector pin or sleeve as it is advanced out of the movable mold half could result in costly damage to the mold cavity in the slide or to the ejector pin or sleeve.
Various slide retainers have been developed to hold the slides in the open position and release the slides upon application of sufficient force, such as the force exerted on the slides by the cam pins advancing into the inclined bores of the slides as the mold halves are closed. It is well known to use a spring loaded ball plunger and detent system as a slide retainer. The ball plunger being mounted in a bore formed either in the inner surface of the slide or the outer surface of the mold half to which it is attached, and the detent is formed on the other surface. U.S. Pat. No. 4,765,585 discloses a slide retainer for injection molds generally comprising a variation of a ball plunger and detent system. U.S. Pat. No. 4,768,747 discloses a slide retainer generally comprising a clip having flexible jaws adapted to releasably engage a pin or dowel mounted on a slide to hold the slide in the open position.
Although existing slide retainers do function to releasably hold a slide in an open position until the mold is closed, the existing slide retainers do not provide feedback to verify that the slide is actually in the open position. It is known to mount switches externally of the mold halves with actuators mounted on the slides so as to engage and actuate the switch upon opening of the mold and it is also known to mount switches on a mold half adjacent the outermost position of a slide in the open position such that the switch is actuated by advancement of the slide to the open position. However, because such switches are mounted externally of the mold or generally exposed during the molding process, they are highly susceptible to damage and malfunctioning.
There remains a need for a system for releasably retaining an injection mold slide in an open position until the mold is subsequently closed and which provides feedback to a controller for the mold to verify that the slide is in the open position.